// Copyright (c) 2002 Graz University of Technology. All rights reserved.
// 
// Redistribution and use in source and binary forms, with or without modification,
// are permitted provided that the following conditions are met:
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// 1. Redistributions of source code must retain the above copyright notice, this
//    list of conditions and the following disclaimer.
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// 2. Redistributions in binary form must reproduce the above copyright notice,
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//    include the following acknowledgment:
// 
//    "This product includes software developed by IAIK of Graz University of
//     Technology."
// 
//    Alternately, this acknowledgment may appear in the software itself, if and
//    wherever such third-party acknowledgments normally appear.
// 
// 4. The names "Graz University of Technology" and "IAIK of Graz University of
//    Technology" must not be used to endorse or promote products derived from this
//    software without prior written permission.
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// 5. Products derived from this software may not be called "IAIK PKCS Wrapper",
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package ostt1_TokenLib;

import java.security.NoSuchAlgorithmException;
import java.security.Signature;

import iaik.asn1.structures.AlgorithmID;

/**
 * This class is an adapter to enables an application to use a different
 * implementation than the standard implementation with the IAIK-JCE.
 */
public class AlgorithmIDAdapter extends AlgorithmID {

	/**
	 * The delegate object to use, if no concrete implementation is set for a
	 * certain engine class.
	 */
	protected AlgorithmID delegate_;

	/**
	 * This is the signature engine to use for this object.
	 */
	protected Signature signatureEngine_;

	/**
	 * Creates a new AlgorithmIDAdapter that uses the given delegate object
	 * to get the .
	 *
	 * @param delegate The object to get other implementations from,
	 *                 implementations not provided by this object.
	 * @preconditions
	 * @postconditions
	 */
	public AlgorithmIDAdapter(AlgorithmID delegate) {
		super(delegate.getAlgorithm());
		delegate_ = delegate;
	}

	/**
	 * Set the implementation to use as signature instance.
	 *
	 * @param signatureEngine The implementation of the signature class to return
	 *                        upon a call to getSignatureInstance(). If null, the
	 *                        implementation is unset.
	 * @preconditions
	 * @postconditions
	 */
	public void setSignatureInstance(Signature signatureEngine) {
		signatureEngine_ = signatureEngine;
	}

	/**
	 * If a concrete signature implementation was set using
	 * setSignatureInstance(Signature), this method returns this. Otherwise, it
	 * delegates the call to the delegate of this object.
	 *
	 * @return The signature engine to use for this algorthim.
	 * @exception NoSuchAlgorithmException If there is no signature
	 *                                     implementation for this algorithm.
	 * @preconditions
	 * @postconditions
	 */
	public Signature getSignatureInstance()
	    throws NoSuchAlgorithmException
	{
		return (signatureEngine_ != null) ? signatureEngine_ : super.getSignatureInstance();
	}

	/**
	 * If a concrete signature implementation was set using
	 * setSignatureInstance(Signature) and the provider name is null, this method
	 * returns this set signature implementation; otherwise, it delegates the call
	 * to the delegate of this object.
	 *
	 * @return The signature engine to use for this algorthim.
	 * @exception NoSuchAlgorithmException If there is no signature
	 *                                     implementation for this algorithm.
	 * @preconditions
	 * @postconditions
	 */
	public Signature getSignatureInstance(String providerName)
	    throws NoSuchAlgorithmException
	{
		return (providerName == null) ? getSignatureInstance() : super
		    .getSignatureInstance(providerName);
	}

}
